1. Field
The present application relates to wireless communication technology and, more particularly, to systems and methods for using variable constraint length encoders.
2. Background
Wireless communication systems are widely deployed to provide various types of communication including voice, multimedia, video, audio, data, and so forth. In some wireless systems, orthogonal frequency-division multiplexing (OFDM) is implemented, which advantageously provides improved transmission in the presence of severe channel conditions, resilience to radio frequency (RF) interference, and lower multi-path distortion. In OFDM, each subcarrier is selected to be orthogonal to each of the other subcarriers. Orthogonality beneficially avoids adjacent subchannel interference and allows efficient modulator and demodulator implementation using fast Fourier transforms (FFTs). The data to be transmitted (e.g., the information bits) are encoded with a particular coding scheme to generate coded bits (e.g., via a convolutional encoder), and the coded bits may further be grouped into multi-bit symbols that are then mapped to modulation symbols based on a particular modulation scheme (e.g., quadrature amplitude modulation or phase shift keying). At each time interval that may be dependent on the bandwidth of each frequency subchannel, a modulation symbol may be wirelessly transmitted on each of the frequency subchannels to a receiver. At the receiver, the received modulated symbols are demodulated and decoded (e.g., via a convolutional decoder).
Communication protocols capable of providing high data transfer rates are becoming available. Ultra-wideband (UWB) technologies are emerging that provide large bandwidth able to deliver high data rates over short distances. For example, the ECMA-368 “High Rate Ultra Wideband PHY and MAC Standard” incorporates a physical (PHY) layer radio based on multi-band OFDM and a media access control (MAC) layer that enables high speed, low power consumption data transfers in the 3.1 GHz to 10.6 GHz RF band in a wireless personal area network (WPAN). Data transfer rates up to 480 megabits per second (Mbps) are provided by the ECMA-368 Standard.
There is increasing demand for efficient, low power consumption, high data rate wireless transfers of voice and multimedia data. However, increasing data rates often result in increases in power consumption, which is especially problematic for battery powered devices, such as wireless handsets.